ALT Coronation Facts: King Charles III will be the 40th monarch to swear the traditional Oath of Faithful Service 2.2kg: weight of the solid gold St Edward's crown, used at the moment of Coronation. Westminster Abbey: Britain’s Coronation church since 1066. King Charles III has become head of the Commonwealth, an association of 56 independent countries and 2.5 billion people. For 14 of these countries (Commonwealth Realms), as well as the UK, the King is head of state. 50 years: A champion of environmental issues for over 50 years, The King first spoke publicly about his concerns on pollution and plastics and their impact on the natural world in 1970. 800 charities: As Prince of Wales, His Majesty became President or Patron of over 800 charities and initiatives in total. More than 6,000 men and women of the UK’s Armed Forces – and nearly 400 Armed Forces personnel from at least 35 Commonwealth countries – will take part in the Coronation.